The present invention relates to the obtaining of vanillic acid and vanillin by bioconversion.
At the present time, vanillin is the flavouring most widely used in the agri-foodstuffs industries. However, the production of natural vanillin from vanilla pods covers only 20% of the market requirements, and its production cost is of the order of 25,000 FF/kg.
Vanillin may also be obtained by chemical synthesis; however, this method of obtaining the product, while suitable for the manufacture of perfumes and cosmetics, may give rise to legislative problems in the agri-foodstuffs industries. In addition, synthetic flavourings tend, moreover, to be less well liked by consumers than flavourings of natural origin.
Accordingly, an effort is being made to obtain aromatic compounds produced by means of biological processes, which employ microorganisms (bacteria, yeasts, fungi), animal or plant cells or their enzyme systems.
Vanillin is produced by certain plants and microorganisms, especially fungi, where it constitutes one of the degradation products of precursors containing an aromatic ring (ferulic acid and vanillic acid).
European Patent Application 453 368 in the name of the company PERNOD-RICARD describes the production of natural vanillin by bioconversion of ferulic acid or vanillic acid in the presence of a filamentous fungus of the Basidiomycetes group, Pycnoporus cinnabarinus.
In this fungus, four metabolic pathways of conversion of ferulic acid have been identified:
Pathway 1: ferulic acid is reduced to coniferyl aldehyde and then to coniferyl alcohol; thereafter different dimers are formed from this compound. This is a minor pathway.
Pathway 2: cleavage of the propenoic chain of ferulic acid takes place, with the loss of two carbons and formation of vanillic acid.
Pathway 3: the vanillic acid resulting from pathway 2 is reduced to vanillin by the reductase I. The vanillin produced may then be reduced by the reductase II to vanillyl alcohol.
Pathway 4: the vanillic acid resulting from pathway 2 is hydroxylated and decarboxylated to methoxyhydroquinone by the action of an intracellular vanillate hydroxylase.
Under the conditions described in Application EP 453 368, the production of vanillin by P. cinnabarinus MIC11 from 300 mg/l of ferulic acid is at most of the order of 45 mg/l (molar conversion yield of 20.5%), and from 300 mg/l of vanillic acid this production is at most of the order of 81.4 mg/l (molar conversion yield of 31%).